1. Field of the Invention
The present invention relates to rotating electrical machines such as electric motors and generators.
2. Description of Related Art
The tightening regulations on the exhaust gas emission to cope with soaring oil prices and global warming have activated development of electric vehicles and hybrid electric vehicles that use rotating electrical machines such as motors and generators.
Conventional distributed winding stators for these rotating electrical machines include those stators of a lap winding format as disclosed in, for example, JP H08-298756A and JP 2005-51981A. Such a lap winding stator is constituted as follows. A rectangular wire is wound into individual oblong coin-like coils (i.e., ellipse-like coils having two parallel linear sides bridged by round ends; hereafter referred to as ellipse-like coils). Each of the ellipse-like coils is fixed in whole and the fixed wires are subjected to torsional deformation. The coil ends of each coil are formed into a non-interfering format for double layer winding. The individual coils thus obtained are inserted in respective slots to provide a lap winding stator.
A coil for use in a rotating electric machine in the related art is disclosed in, for example, JP S64-1444A. The coil is formed as follows. That is, a temporary fixation tape is wound around an original form coil having a pair of linear regions thereof that are to constitute coil sides of a final coil using a film insulator composed of a wound thermoplastic film. Then, only the linear regions of the original form coil is introduced into an ultrasonic welding apparatus equipped with a fixing apparatus to weld the insulator film of the wire and an insulation tape for insulation from ground is wound. The thus insulated coil is then inserted into a slot.
The conventional distributed winding stator, however, is manufactured by winding and deforming coils one by one. This makes it necessary to provide wire terminals twice the number of the coils and arrange and weld the wire terminals onto the side or top part of the coil ends. This results in an increase in the size of the coil ends, so that it has been difficult to provide compact connection and arrangement of the wire terminals.
Two slot insertion regions of the lap winding coil that are to be inserted into slots are arranged in different slots of the stator, so that they could not be inserted the slots without undergoing elastic deformation. When the lap winding coils are continuously formed, the coils pull each other, resulting in an increase in difficulty of the operation of inserting the coils into the slots. For these reasons, a certain gap (0.1 to 0.2 mm or more) is required between the two coils in order to assemble a continuous lap winding coil of a flat wire with insulation into a slot of the stator. This delimits the space factor and heat dissipation performance of the coil.
In the case of inserting a coil into a slot of a rotating electrical machine, it is desirable that a coil in whole has a flexibility upon deformation of the coil into a shape suitable for inserting it into the slot after having been formed into a wound shape. However, when the coil is inserted into the slot after the deformation, it is necessary to fix the slot insertion region of the coil so that it will not loosen or feaze. The conventional technology would not have sufficiently taken account of achieving a good balance between the two properties.